The Hard-Mounted Hollow Retroreflector™ (HMHR) is a self-compensating mirror that is totally insensitive to position and movement, such as tilt.

Parallel incident light that hits the HMHR will be returned with great accuracy to the light source, regardless of the HMHR's physical orientation.

The HMHR is constructed of three first-surface mirrors assembled by a proprietary process into a mutually-orthogonal inside corner. The mirrors can be coated for maximization over a spectral range, from UV to far IR. This configuration eliminates material absorption and chromatic aberration. The mirror assembly of the HMHR is mounted on an Invar mount. (5.0"/127mm unit comes with aluminum mount). Invar is a low-expansion (CTE 0.75) alloy of iron and nickel that is used when control of thermally-induced dimensional change is required.

Stability and Accuracy

The HMHR offers properties which makes it especially suitable for critical applications, such as Michelson interferometers. The mount maintains stability of the distance between the apex of the corner cube and the back surface of the mount, as well as concentricity of the apex with respect to the mounting thread. HMHRs can also be provided in matched pairs for better modulation.

* Beam Deviation is the maximum deviation from parallelism, expressed in seconds of arc, of any single return beam from any of the 6 sub-apertures of the retroreflector, when the retroreflector is fully-illuminated.